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How to Tell When Your Oxygen Level Is Low?

Causes of low oxygen levels in the blood, hypoxemia, vary greatly from carbon monoxide, chemical and/or irritant exposures filling the lungs and blocking their ability to absorb the oxygen needed for healthy cell function to a wide range of medical conditions that obstruct air flow and interfere with the respiratory system or block blood flow and interfere with the circulatory system 2. Without enough oxygen, the body breaks down and hypoxemia can even cause organ and tissue harm/failure or death. You can tell if your oxygen level is low through a few tests and simple observations.

Ask your doctor for an arterial blood gas (ABG), a blood test to confirm the oxygen and carbon dioxide concentrations in your blood.

Heart Rate & Respiration in Children

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Stand up, sit down and lie flat to test for low oxygen levels. If you experience shortness of breath, dizziness or confusion while in any or all of these positions, you likely have low blood oxygen levels.

Review your exercise routine. If you have hypoxemia during or after exercise, you will find that you're suddenly slower when exercising, less coordinated and/or fatigued. As these symptoms could result from severe respiratory or circulatory issues, stop your routine and address your concerns with your doctor. In addition, review your sleep schedule/sleep disturbances (sudden waking, snoring, dry mouth or shortness of breath) and compare to any new onsets of fatigue to see if a correlation exists. If it does, you may have reduced flow of oxygen to the lungs causing temporary breathing interruptions (sleep apnea) from an airway obstruction, narrow throat, or other health condition.

What Is a Normal O2 Saturation Level?

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Check your finger and toe nails and beds and your lips for a blue to purplish discoloration (cyanosis) if you experience any other symptoms of hypoxemia or have a bluish tint to your skin. Cyanosis occurs when your blood oxygen level drops causing blood discoloration that appears blue or purplish through the skin. For example, think of a child who holds her breath as part of a competition with other children. She stops the flow of air into her lungs and the resulting blood oxygen loss causes her blood to turn from bright red (normal) to dark red (low) and her lips and mouth change to blue/purple or, in severe cases, turn white.

Test your blood oxygen saturation and pulse with a pulse oximeter. An oximeter sends two beams of light through a fingertip or earlobe to determine the color of your blood—bright red color (normal if 95 to 100 percent at sea level), dark red (low if under 90 or severe under 80).


Always see your doctor if you have undiagnosed shortness of breath during any activity and/or seek immediate emergency attention if you have symptoms of hypoxemia with white lips as you may have a serious health condition.